Construction Of Tumor Microenvironment Responsive LDHs Nanocomposite For Cancer Diagnosis And Treatment

The tumor microenvironment is characterized by weak acidity,overexpressed H₂O₂,and accumulation of lactic acid,which not only affects tumor proliferation,metastasis,and apoptosis,but also provides an opportunity for tumor therapy based on specific environmental regulation.Therefore,how to develop efficient tumor-specific response cancer precision therapy is the key to prolonging the lifespan of patients.Chemodynamic therapy（CDT）mainly utilizes excess H₂O₂ in the tumor microenvironment to react with transition metal compounds to generate reactive oxygen species with strong oxidizing properties,thereby causing apoptosis and necrosis.With the development of nanotechnology,the rational design of nano-therapeutic agents responsive to the tumor microenvironment brings hope for the precise treatment of cancer.LDH（Layered Double Hydroxide）can accurately respond to the acidity in the tumor microenvironment.Furthermore,MgAl-LDH has been approved by the FDA as a drug for the treatment of gastric acid,which provides the possibility for its further clinical application.Inspired by this,based on the confinement effect and the topological transition effect of LDHs,three nano-reagents A@P/uLDHs,ATX/LDH and FP@5-MMO were constructed,respectively.The tumor microenvironment（TME）in situ catalyzes/triggers/enhances specific chemical reactions to generate reactive free radical species,controllably adjust the direction and rate of chemical reactions,and ultimately achieve a significant improvement in anti-tumor activity.In addition,the influence of the tumor microenvironment on the material structure and antitumor activity was systematically analyzed by various characterization methods.This study provides new strategy for the design,preparation,and performance regulation of novel CDT therapeutic agents.The main research contents and results of this study are as follows:1.Based on the unique two-dimensional confinement effect of LDHs,organic/inorganic nanohybrids system A@P/uLDHs was constructed by supramolecular self-assembly.The dispersion and stabilization of the artemisinin molecules on the surface of the LDHs layers not only improves the dispersibility of artemisinin molecules in water,but also endows them with the ability of passively target tumor sites.Through various characterization methods,it was proved that the A@P/uLDHs nanoagent can release artemisinin molecules under the simulated TME（weak acidity）,and consumed glutathione to release Fe²⁺,which further interacted with artemisinin molecules.The cleavage of the peroxy bridge can generate abundant reactive free radicals.In addition,abundant ROS can be generated by Fe²⁺catalytic Fenton reaction.The depletion of glutathione as well as the accumulation of Fe²⁺and lipid peroxides in cells can lead to ferroptosis and enhance the toxicity of CDT.In vivo experiments further demonstrated that A@P/uLDHs exhibited good antitumor effects under tumor microenvironment conditions.This work provides a new strategy for improving the performance of CDT to inhibit tumor proliferation and metastasis.2.Based on the confinement effect of LDH layers,astaxanthin molecules were anchored on the surface of NiFe-LDHs nanosheets,and a multifunctional nano-autocatalytic reaction system ATX/LDH was successfully constructed.NiFe-LDHs nanosheets have abundant hydroxyl groups and positive charges,which is beneficial to the uniform dispersion of astaxanthin molecules on the surface of LDHs,thus improving the stability of astaxanthin molecules.Through ESR,FT-IR,UV-Vis absorption spectroscopy and other tests,it was confirmed that the ATX/LDH nanocatalyst exposed a large number of unsaturated Fe active sites through partial biodegradation of the ATX/LDH nanocatalyst under the simulated tumor microenvironment.ATX/LDH can self-sensitized to generate free radicals through the proton-coupled electron transfer process when ATX chelated with the unsaturated Fe active site.More importantly,compared with free Fe²⁺,these unsaturated Fe sites greatly promote the deprotonation efficiency during free radical generation due to the existence of Br（?）nsted basic sites in LDHs laminates,which can significantly improving the radicals generation.The nanoagent demonstrated effectively tumor proliferation inhibition via both in vivo and in vitro experiments,which provides a theoretical basis for the application of the functional reversal of tumor microenvironmental response-harmless and harmless switching behavior for CDT.3.Based on the unique topological transition effect of LDHs,a high-entropy oxide 5-MMO（denoted as FP@5-MMO）with spinel structure containing five transition metal elements was successfully constructed,followed by the modification of FA-PEG on the surface.This nanomaterial has various biological enzyme activities（POD,OXD,and GSH oxidase,etc.）,so it can be used as a nanozyme in CDT in response to tumor microenvironment.The coexistence of various transition metal elements enhances the d-d band transition,which in turn improves the absorption of photons by the nanozyme,broadens the absorption of the nanozyme to the NIR-Ⅱ region,and realizes the NIR-Ⅱ light-driven photothermal-promoted enzyme activity reaction.UV-Vis and ESR can confirm that this nanozyme can catalyze H₂O₂ to generate ROS（such as·OH and·O₂^-）under the stimulate of TME,and the ROS yield was significantly improved under light irradiation in the NIR-Ⅱ region.Even in the absence of H₂O₂,ambient O₂ can be catalyzed to generate·O₂^–,which greatly reduces the over-dependence of CDT system on H₂O₂.Both in vitro and in vivo experiments can demonstrate that the nanozyme has the high efficiency of antitumor activity.This work further expands the research scope of multifunctional catalytic chemical reaction nanosystems,and broaden the application of high entropy oxide in biomedical domain.